Check valves are commonly used in numerous military and aerospace operations where dependable sealing and operating functions are required under demanding conditions. In typical check valves, a spring loaded valve member is located on a common longitudinal axis in a valve body or valve housing between an inlet port and an outlet port. A floating "O" ring seal on the valve member is used to establish contact with metal sealing surfaces of the valve member and a valve seat in the valve body to cushion closing of the valve and to insure perfect sealing. Fluid flow in one direction pushes the valve member open when the pressure exceeds a determined value which overcomes a closing force of a spring acting on the valve member. In the absence of sufficient differential pressure across the valve member or fluid flow in a reverse direction, the spring force seats the "O" ring on the valve member in a contact condition on the valve seat and prevents fluid flow. The valve member is arranged relative to the valve housing to compress the "O" ring sufficiently to engage metal sealing surfaces. The valve member is arranged to have a metal-to-metal contact with the valve housing to prevent extrusion of the "O" ring with an excess pressure differential. The valve member also has a guide extension slidably received in a guide bore in the valve housing to guide the valve member for to and fro motion along the longitudinal axis of the valve housing.
Because of the spring and the mass of the valve member, fluid flowing though the valve can cause a harmonic motion to occur at a natural frequency of the valve member which, over a period of time, results in accelerated wear of the valve member and its guide extension and guide bore. This is a common effect in gaseous fluid service and can ruin a valve in a matter of hours in some instances.
The wear of the valve member and its guide valve member extension and guide bore also increases the clearance between these two parts and the valve member can tip or wobble about its longitudinal axis which accelerates its wear and can ultimately cause the valve member to jam and the valve will fail.
The harmonic motion of the valve member can also introduce an undesirable disturbance in the consistency of fluid flow through the valve.
The accelerated wear of the valve member also can cause particulates to be generated in the fluid stream which can be deleterious to use of the fluid stream or can alter its characteristics.
Thus, a check valve can have regions of operating instability which a user must avoid because there is no damping mechanism for the vibration of the valve element during operation.
In pressure regulators sometimes a damper is incorporated in the form of a bellows-sealed chamber that breathes through one or more orifices as it is forced to change volume by motion of the valve member. In this type of system, the bellows is not very effective for damping and has a limited life. Small breather orifices are also subject to contamination or plugging in use.